1. Technical Field
This invention is directed toward a system and method for very low bandwidth transmission of video imagery. More specifically, the invention is directed toward a system and method for very low bandwidth transmission of video imagery of faces that are talking.
2. Background Art
Voice only communication lacks many of the nuances of face-to-face communication. The most obvious lack is that of facial expressions. Video conferencing is aimed to overcoming this, but is hampered by the high bandwidth cost to achieve quality video image transmission. Due to this high bandwidth requirement, and its associated costs, current commercial video teleconference solutions are limited in their usage.
Meanwhile, much research has been done for low bit-rate face video coding. One class of method is model-based coding, such as the MPEG-4 face animation standard. In these methods, a facial image is coded as changes of face model parameters so that a very low bit-rate can be achieved. However, it is difficult to make the synthesized face model look natural and match the input video. Many existing model-based coding systems either use 3D face models or use principal component analysis. The drawback with using 3D modeling is that currently it is difficult to obtain a good 3D model, to track poses, and to generate facial expressions. The PCA approach also has a strong requirement for per-pixel alignment, necessary to avoid blurry images, which is difficult to obtain.
Compared to model-based techniques, traditional waveform based coding techniques (such as H.26X, MPEG-1/2/4, and so on) are fully automatic and robust. However, the quality of low bit-rate video is usually not sufficient to support these techniques. The computational complexity for a sophisticated waveform video coder, such as H.264, can also be very high.
It is noted that in the remainder of this specification, the description refers to various individual publications identified by a numeric designator contained within a pair of brackets. For example, such a reference may be identified by reciting, “reference [1]” or simply “[1]”. A listing of the publications corresponding to each designator can be found at the end of the Detailed Description section.